There has been known, as an acoustic wave device using an acoustic wave, a surface acoustic wave device including an IDT (Interdigital Transducer) composed of a pair of comb-shaped electrodes located on a piezoelectric substrate. The surface acoustic wave device is used for filters in various types of circuits, as typified by, for example, mobile phones, that process radio signals in a frequency band of 45 MHz to 2 GHz.
In recent years, as communication devices such as mobile phones are sophisticated (for example, multi-band support, multi-mode support), it has been studied to decrease the loss of the filter to increase the receiving sensitivity of the communication device and to reduce the electrical power consumption. For example, it has been suggested to embed an insulating material between the tip of an electrode finger and a bus bar or the tip of a dummy electrode finger as disclosed in, for example, Japanese Patent Application Publication No. 2009-278429.
However, the conventional surface acoustic wave device has room for improvement in reducing the loss.